Brillouin scattering was used to investigate the elastic properties of calcium alumino-silicate glasses. The Brillouin frequency shifts, along with the measurements of density and refractive index, allowed the calculation of sound velocities and elastic constants. The values of elastic moduli (including Young's modulus, bulk modulus, shear modulus, and Poisson ratio), derived from experimental data for our glasses, were much larger those for pure SiO2 glass. These values were compared with those calculated in terms of existing theories.